4-Way Fully- Ported Stem Valves

4-way fully-ported valves have two inlets, two outlets and one exhaust port. When the stem is in one position air flows from one inlet to its outlet while the other inlet is blocked. Moving the stem to the opposite position reverses this action. This may be defined as two 3-way valves, one Normally-Closed and one Normally-Open operating simultaneously. 4-way fully-ported stem valves may either be spring return or double acting. A double acting stem must be moved from one position to the other, a spring return stem will move to the opposite position when released.